Airbag devices are generally known and used as a passive restraint device consisting of bags which are inflated with gas to restrain the driver and passengers during a collision. Some known airbag devices have an aspiratory function to accelerate deployment of the airbag by drawing the surrounding air into the airbag by suction created when the gas discharged from an inflator flows into the airbag. Typical examples of such airbag devices are disclosed in Japanese Patent No. 3275771 (corresponding to JP-10297411-A) and Japanese Patent Laid-Open Publication (JP-A) No. 9076866.
The airbag device disclosed in JP-10297411-A is a side airbag device and, as shown here in FIG. 39, the side airbag device 300 includes an airbag 301 having an upper part 302 provided for protection of the chest of a vehicle occupant, a lower part 303 provided for protection of the abdominal part of the occupant, and an attachment part 304 formed integrally with a rear portion of the lower part 303 for attachment of the airbag 301 to the frame of a seat back (not shown). The attachment part 304 accommodates within it an inflator 306. The inflator 306 is disposed vertically and has a nozzle at a lower end hereof. The airbag 301 has an opening 305 formed in an upper end portion of the attachment part 304 for adjusting internal pressure of the airbag 301. The opening 305 is disposed upstream of or on an opposite side of the nozzle of the inflator 306.
With this arrangement, when the inflator 306 is activated or fired to inflate the airbag 301, the surrounding air is drawn from the opening 305 into the airbag 301 by suction created when gas discharged from the inflator 306 flows into the airbag 301. By thus taking the surrounding air into the airbag 301, the side airbag device 300 performs an aspiratory function to accelerate the deployment of the airbag 301. However, due to the location of the nozzle of the inflator 306, the gas discharged from the inflator 306 first flows in a horizontal direction, then advancing vertically upward through the lower part 303 of the airbag 301. By thus taking a bent flow path, the gas flow cannot obtain a sufficiently high speed to create a suction which is high enough to take in a sufficient amount of surrounding air through the opening 305 into the airbag 301. Thus, only a limited aspiration effect can be attained.
FIG. 40 hereof shows an airbag device 310 disclosed in JP-9076866-A. The airbag device 310 includes a module case 311 disposed in a dashboard or instrument panel of the vehicle, an inflator 312 received in the module case 311 for inflating an airbag 314 connected to an open end 313 of the module case 311. The module case 311 has a plurality of openings 315 and a corresponding number of baffle plates 316 projecting obliquely into the module case 312 from respective peripheral edges of the openings 315. The openings 315 and the inclined baffle plates 316 are located between the inflator 312 and the airbag 314 so that the surrounding air can be drawn from the openings 315 into the airbag 314 due to suction created when gas discharged from the inflator 312 flows into the airbag 314.
With this arrangement, however, since the flow of gas generated from the inflator 312 is not stable due to the presence of the baffle plates 316, and since the openings 315 provide a relatively small open area, only a limited aspiration effect can be attained by the airbag device 310.
It is accordingly an object of the present invention to provide an airbag device which is capable of achieving an aspiration effect efficiently to speed up the deployment of an airbag.